Selective deactivation of cylinders in multiple cylinder internal combustion engines is known in the art. For example, it is known in eight cylinder engines to selectively deactivate two or more cylinders during light bad conditions. Such deactivation of cylinders can therefore increase fuel efficiency. Various devices are known in the art to deactivate combustion chamber valves for improving fuel efficiency during specific engine load conditions.
Older systems have proposed to deactivate cylinders by simply cutting off the supply of fuel to selective cylinders. However such systems suffer from the drawback that each deactivated cylinder continuously imports, compresses, and expels unignited air significantly reducing the efficiency of the engine. It was then suggested to selectively deactivate cylinders by deactivating the valve assembly to eliminate the continuous pumping by the deactivated cylinders. One such system proposed to cut off an entire bank of a six-cylinder engine and utilized an additional complicated mechanical device to hold open the exhaust valves to eliminate losses previously endured during the compression stroke. Other complicated mechanical valve drive solutions have also been suggested which heretofore have not provided a viable solution to cylinder deactivation.
It is also known to provide a roller hydraulic lifter valve between a cam and a rocker arm in a conventional cam in head driven valve assembly in an internal combustion engine. A hydraulic cam follower is mounted to the head of the engine and disposed between the cam and the rocker arm. A source of pressurized oil is provided to the hydraulic lifter to provide zero lash adjustment and is conventional in the art. When the valve closes, oil flows into the tappet body to urge a lifter pushrod to contact the valve train and take up any clearance. As the camshaft pushes on the lifter a check valve may be closed to seal the oil inside the lifter such that the lifter then acts as a solid unit.
Accordingly, it is an object of the present disclosure to provide a simple means to selectively deactivate valve operation of specific cylinders during certain engine load conditions while reducing risk of surface damage to the cam lobes. It is further desirable to provide a deactivation means which requires few changes to existing components and may be employed within the existing space occupied by conventional valve-train components.